It is common practice in video production to use a dissolve region to concatenate two scenes. In such a region, the second scene gradually appears while the first scene gradually fades out, and by the end of the dissolve region, the second scene completely replaces the first. Although dissolve regions can be up to several seconds long, dissolves of 1/2 to 1 second are more common in video production. The dissolve process is typically called cross-fade.
Attempting to compress a dissolve region via image compression using a typical motion compensation algorithm results in a high entropy prediction error image. Encoding such an error image requires more bits than usual, which may not be affordable for all frames of a dissolve region without increasing the average bit-rate. An image that is encoded with an insufficient number of bits may appear blocky when it is decoded. The visibility of the blockiness may vary depending on the length of the dissolve region. Such blockiness can be eliminated by first detecting dissolves, then encoding the frames in a dissolve region in a proper or different way.
It is an object of the present invention to provide a method and apparatus for detecting dissolve regions and boundaries within digital video sequences.
Further objects and advantages of the invention will become apparent from the description of the invention which follows.